A Tustin, Calif., woman is suing a veterinary office for $1 million, alleging they used extortion by threatening to report her for animal cruelty when she couldn't pay for a $10,000 surgical procedure for her dog.

Karen Kelly's dog, Mojo, was hit and dragged under a car on July 31, 2011, Kelly claims in a lawsuit filed with the California Superior Court in Orange County. She rushed the dog to Advanced Critical Care and Internal Medicine Inc., a 24-hour veterinary facility in Tustin, the court filing states.

She signed an estimate and authorization for services after being asked to do so, according to the lawsuit. She was told "immediate surgery" was needed to save Mojo's life, costing $10,000, but "that there was no guarantee that Mojo would survive the surgery," according to the court filing.

She explained that she did not have $10,000 and called several friends to see if they could come up with the money, but none could, states the lawsuit, which adds one friend applied for credit at the center and was declined.

Kelly, who is suing for civil extortion, intentional infliction of emotional distress and negligent infliction of emotional distress, declined to comment to ABC News and directed questions to her attorney.

Her attorney, Barry Besser, said he is investigating which veterinarians from the practice, which was bought by new owners and renamed in 2012, will be named as defendants. Until then, the lawsuit has not yet been served.

The veterinarian who saw Mojo, according to the dog's medical record, Dayna Zane, no longer works at the location and declined to comment to ABC News.

One of the alleged former owners of Advanced Critical Care and Internal Medicine Inc. did not respond to multiple requests for comment.

Kelly, according to the lawsuit, "then insisted that she be allowed to go home and bring back a check, but the defendants refused, "stating that they were afraid [Kelly] would abandon the dog and not come back." She also asked to bring Mojo home that day so she could bring the animal to her own veterinarian in the morning, the filing states.

The defendants refused, giving her "three options," the court filing states:
"1) Put the dog to sleep
2) Pay the $10,000
3) Keep the dog in critical care overnight, which would cost $1,500 in addition to what the defendants were going to charge [Kelly] for what they had already done, which was in the sum of $1,308.75."

The defendants also told Kelly that "if she insisted on taking her dog home, that she would have to sign a form that it was against" their medical advice, "and that they were going to report her to the authorities for 'animal cruelty,' which is a crime," the lawsuit states.

In the lawsuit, Kelly claims she did not have the funds to pay the $1,308.75 bill. She was "required to and forced to sign an agreement to pay said amount in full the very next day, or she would be turned over to collections," the lawsuit states.

"[Kelly] signed the agreement under severe duress, as that was the only way that she could get her dog back, even though she knew that she would not be able to pay the entire amount in full by the following day," the lawsuit states.

Dr. Peter Weinstein, executive director of the Southern California Veterinary Medical Association, said most veterinarians understand the cost of veterinary care is something for which many people do not budget.

"Beyond the animal's basic welfare, any surprises like dog poison, getting hit by a car or eating panty hose, can run into specific costs and is not expected," he said. "We hope to work with pet owners so a pet gets the best care possible, understanding the cost of providing care."

Weinstein said many people don't fully understand the cost of human health care, if they are exposed mainly to insured care, and are surprised by the cost of animal medical care.

"When you try to compare apples to apples, it is really hard to do," he said. Only a small percentage of pet owners have health insurance for their animals.

Weinstein added that veterinary practices fit more into small business than health care centers for people, and typically require upfront payment, usually cash, check or credit card. However, many veterinarians, including himself, have accepted bartering for owners over time who can not afford to care for their animals' medical care.

"I got signed litograph from an artist for neutering his dog," Weinstein said.

Weinstein adds that pet owners should ask veterinary practices about third party options for payment such as Care Credit.

Weinstein said a misconception that many pet owners have is that veterinary facilities are very profitable.

"Like many small businesses, their overhead costs are huge and profits are nowhere near where healthcare costs are in other parts of the field," Weinstein said.

After Mojo was released to Kelly, she received a final notice from the defendants for $1,308.75, which was turned over to a collection agency, the lawsuit states.

The day after Mojo was hit by a car, an agent from the County of Orange animal control came to her home when she was not home and attached a notice to her door, indicating that they were investigating an allegation of animal cruelty. Later animal control dropped the case against her, after, the lawsuit claims, Kelly had "already been put through severe stress and emotional distress."

The dog is still alive, according to Besser. It's unclear what treatment it received after leaving the animal hospital.

Corey Evans, an attorney in San Francisco who focuses on animal issues and is not involved in this case, said under the California Veterinary Medical Practice Act, whether or not an owner is legally obligated to provide medical care for an injured dog depends on the situation.

He said while an animal is typically considered the property of its owner, allowing an animal to suffer may be considered animal cruelty. However, a veterinarian cannot generally keep an injured animal without the owner's permission if the owner wishes to take the dog to another medical facility.

State law indicates that licensees of the Veterinary Medical Board have a "duty" to report animal cruelty if they have "reasonable cause to believe an animal under its care has been a victim of animal abuse or cruelty".

"Everybody who has a dog and cares for a dog has a legal duty not to neglect the dog," Evans said.